The Performance Assessment and Remedial Measures of Bridge Structure
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Date
2019-06
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
The bridge is an infrastructure which built across the river also used to pass safely from one
side of the road to another to cross the river; on the road shall be kept strong to serve intended
purposes. The bridge structure requires detail, assessment before and after construction both
due to possible failures. Many countries have come upon different mitigation measure to
overcome failure by providing bridge assessment. Ethiopian Road Authority follows up bridge
structure failure by recording all necessary data about bridge and Road situation.
The Bilate River Bridge is the one among those encountered local abutment failure.
The abutment failure of the bridge was seen at different times, which is observed in the field
assessment. The analysis was conducted on the abutment scour failure for a different return
period of time. The existing bridge opening size was the 26m length, 5m wide. Both sides of
riverbank material were taken and analysis is done in a laboratory result express that particle
diameter of 1.5mm and 34.5mm for D50 and D95 respectively.
The maximum design flood estimation resulted in 284.2m
3
/s, and 327.3 m
3
/ at the Bilate River
for 50-year and 100-year return period respectively. In the design flood estimation rainfallrunoff
model
analyzed
by
Initial
and
constant
loss
method
and
direct
runoff
by
the
SCS
unit
hydrograph
method
also
base
flow
by
recession
method.
The
Bridge
instability
evaluated
by
HEC
RAS
5.0.1;
has
been
prepared
by
taking
inputs
like;
river
cross
section,
design
flood,
and
riverbank
materials.
The
local abutment
scouring
observed
in
the
vicinity
of
the
structure
of the
bridge
incorporate
with
overtopping
which
endures
Bridge to
fail.
The
model
results
show
that
dominate
cause
of
abutment
scours
of
the
bridge
was
an
inadequate
opening
size
to
pass
design
flood
at
the
bridge;
because
of
constriction
at
the
bridge
within
the
river
has resulted in an increase the flow velocity so that, the abutment has been scoured.
Countermeasures were reviewed based on the hydraulic analysis result calculated. Based on
hydraulic analysis results; the recommended river training work and increase the opening size
of a bridge across the river.
Description
Keywords
Design Discharge, HEC-HMS, Hydraulic analysis, HEC-RAS, scour, Bilate, Bridge